I’m working with a few scholars on non-book, digital scholarship projects where a book would not suffice and so they’re turning to other forms to meet the needs/goals of the intended work. In two instances, a book is the argument wanted, but these “books” would need to be heavily connected to previously inaccessible materials and so the argument requires building and curating an archive along with the traditional long-form, text-based argument. So, for these two scholarst, it makes the most sense to envision their projects as curated digital archives and digital scholarship projects that will be published first, with book-like versions coming as secondary forms.
Right now, without knowing what your book might be about, I’m interested in your process to think through the argument and select the form. I think seeing this thinking and working through would be of interest and useful for other scholars who are grappling with the same sorts of concerns.